Field of the Invention
The present invention relates to a display control apparatus capable of displaying a plurality of images and a method for controlling the display control apparatus.
Description of the Related Art
There is a conventional digital device that can simultaneously display a plurality of images (e.g., photographs) on the same screen (i.e., an index display screen).
An advanced display device, which is large in screen size and excellent in accuracy, is usable for the above-described index display. Further, the processing ability of a recently available control device and the storage capacity of a storage medium are sufficiently high to simultaneously display many images on the same screen.
In general, a digital device realizing the index display enables users to scroll a plurality of images on a display screen in an arbitrary direction by operating an operation member (e.g., a button, a lever, a rotary dial, or a touch panel).
On the other hand, to display a plurality of images, a significant physical processing time is used to perform processing for reading image data from a storage medium, decoding image data (including decompressing compressed image data), resizing image data according to a display size, and rasterizing image data into a video random access memory (VRAM).
When the index display is performed to simultaneously display a plurality of images, the digital device is used to repetitively perform the above-described sequential processing for each of the plurality of images. Therefore, it takes a relatively long time to complete display preparation processing for all images to be displayed on the same screen.
Hence, a conventional method discussed in Japanese Patent Application Laid-Open No. 2001-231005 includes changing a display order of each image to be displayed on an index display screen according to predetermined conditions, initially displaying the images that have been previously browsed by a user, and prioritizing the display of an image positioned closely to the previously displayed images.
According to the above-described conventional method, the user can surely find the images having been previously browsed immediately after the index display is started.
However, according to the above-described conventional method, if the scrolling is performed on the index display screen, the display of images to be newly displayed according to the scrolling may be delayed because a relatively long time is used to complete the display preparation processing for newly displayed images.
The delay time tends to increase in proportion to the scrolling speed and also increase in proportion to the number of images to be displayed simultaneously. In an extreme case, no image can be newly displayed when the scrolling speed is high.
If the display of the images to be displayed is delayed too much, a user who is performing a scroll operation cannot check an actual state of the scrolling currently in progress and therefore cannot determine the time to stop the scrolling.
Further, even after a user inputs an instruction to stop the scrolling, there is a relatively long waiting time to complete the display processing for the images being not yet displayed.
When the scrolling is performed on an index display screen according to the method discussed in Japanese Patent Application Laid-Open No. 2001-231005, the display of an image positioned closely to the previously displayed images, i.e., an image positioned on an immediately disappearing side with respect to the scrolling direction (which corresponds to a moving direction of the images), is prioritized.
However, the image positioned closely to the previously displayed images is shortly excluded from a display target group, while the scrolling advances, at earlier timing compared to other images newly added to the display target group.
Therefore, the possibility of completing the display preparation processing for the image positioned closely to the previously displayed images before the image is excluded from the display target group is relatively low.
Moreover, the display preparation processing for other images newly added to the display target group is delayed correspondingly because the processing priority order for these newly added images is lower than that of the image positioned closely to the previously displayed images.
Therefore, according to the method discussed in Japanese Patent Application Laid-Open No. 2001-231005, the display preparation processing may be entirely delayed and many of the images to be displayed may not be actually displayed on the index display screen during the scroll operation.